1. Field of the Invention
The present invention relates to a method and apparatus for forming electrodes on an oxide semiconductor wherein the electrical properties of the surface of the oxide semiconductor are improved by preventing formation of junctions between the oxide and electrode material being accompanied by desorption of oxygen from the oxide.
2. Description of the Prior Art
There are two conventional methods used for forming junctions between oxide semiconductor and electrode material on the semiconductor. One method is used to form a junction with bulk oxide semiconductor, and consists of using acid or the like to chemical etch the oxide surface, placing the sample in a vacuum chamber and depositing the electrode material. The other method is used when a junction is to be formed with a thin film of oxide semiconductor, and consists of forming the oxide semiconductor in an oxide film forming apparatus, and then, without subjecting the oxide surface to any particular treatment, moving the sample into an electrode deposition apparatus to form the electrodes. An advantage of these methods is that they facilitate the formation of junctions between oxides and electrode material without the use of special techniques.
However, a major drawback with each of the above methods is that prior to the deposition of electrode material, the oxide surface is exposed to the atmosphere, and as a result the electrical properties of the oxide surface are degraded by carbon dioxide and other such substances in the atmosphere. Thus, the functions of devices using such junctions between oxide semiconductors and electrode material fabricated by the above conventional methods are considerably inferior to devices using junctions between conventional semiconductor and electrode material.
An object of the present invention is to provide a method and apparatus that enables electrodes having superior electrical properties to be formed on oxide semiconductor.